Document databases, such as Apache CouchDB and MongoDB, employ a document data model to store semi-structured and unstructured data. In this model, a document is used to encapsulate all the information pertaining to an object, usually in JavaScript Object Notation (JSON) format, meaning that a single document is self-describing. Since they are self-describing, different documents may have different schema. For example a document describing a movie item, as illustrated in the following JSON file, would have a different schema from a document describing a book item:
[ { "title" : "The Imitation Game", "year": 2014 "metadata" : { "directors" : [ "Morten Tyldum"], "release_date" : "2014-11-14T00:00:00Z", "rating" : 8.0, "genres" ...
